Even with an empty drum my washer is in imbalance, thumps, smoke coming from rear drum/drain vent and bits of rubber in the tub. It is something internal as the rubber is in the tub and the belt is fine.

You have a 10 year warranty on the outer tub and a 20 year warranty on the inner basket. The warranty is for parts only, you still have to pay for the labor. You might be able to get them to send you the parts if you want to fix it yourself. 1-800-GE-CARES.